1. Field of the Invention
The present invention relates to the field of rock drill bits adapted to be mounted on and used with rotary percussive electric and/or pneumatic drills and hammers. More particularly, the present invention relates to a piloted rock drill bit having a central leading pilot drill point for drilling a pilot hole and lagging reaming wings for enlarging the pilot hole.
2. Background
Piloted rock drill bits, for example, as shown and described in U.S. Pat. Nos. 2,532,783; 2,818,292; 2,938,709; 3,145,789; 3,469,641; 4,275,796; and, 4,294,319, are known and are commonly used for drilling holes through hard materials such as concrete, stone, brick, masonry block, rock, etc. (herein collectively referred to as “rock”). These rock drill bits have a central leading pilot drill point for drilling a pilot hole and lagging reaming wings for enlarging the pilot hole. They are adapted to be mounted on rotary percussive drills and hammers (herein collectively referred to as “drills”) which are electrically or pneumatically powered.
In use, the drills typically both rotate the drill bits about their longitudinal axis and, also, vibrate the drill bits along their longitudinal axis. After mounting on a drill, the rock drill bits are directed onto the rock and the rotary and vibratory/percussive action of the bit causes it to drill through/form a hole in the rock. The central leading drill point serves to form the pilot hole and, because the leading drill point projects into and is rotatably captured in the pilot hole, it also serves to guide the lagging reaming wings to concentrically enlarge the pilot hole to the desired size/diameter. The rock drill bits can be provided with central air passageways extending from the drill bit mounting base to openings at the lagging reaming wings. Accordingly, when the rock drill bits are mounted to pneumatic drills, pressurized air can be directed therethrough to the lagging reaming wings whereby rock swarf/waste debris resulting from the drilling (hereinafter referred to as “waste debris”) be blown out of the hole.
The prior piloted rock drill bits, however, have shortcomings and drawbacks. When starting a hole on a flat rock surface, they often skip therealong and are difficult to maintain centered at the desired hole location. Also, the waste debris often plugs the spaces between the reaming wings thereby requiring removal of the drill bit from the hole and cleaning. Moreover, the prior piloted rock drill bits are relatively difficult to manufacture and costly. Accordingly, a need exists for piloted rock drill bits which are relatively easy to maintain centered over the desired hole location when starting a hole, which minimize swarf/waste debris plugging and which are relatively easier to manufacture and less costly.